The federal government’s plan to hold a plebiscite on same-sex marriage is dead.

Labor has officially announced it would not support the plebiscite, which has ended prospects of the vote because there is not sufficient support on the Senate crossbench to carry it.

The decision follows a Labor caucus meeting in Canberra this morning, where members voted to block the bill put forward by the Coalition.

A source inside the Labor caucus indicated the discussion took less than 15 minutes and was resolved unanimously.

The Turnbull government is still expected to introduce the legislation, despite lacking the numbers.

One MP however is threatening to bring down the government if Turnbull backflips.

Nationals member Andrew Broad has said his support for the government is “conditional” on the Coalition honouring all its election promises.

“The government that I am a part of and will remain a part of is conditonal on the fact that the only way that there will be a change to the Marriage Act in this Parliament is a plebiscite,” Broad said. “My position as a member of the government is very clear on that.”

Here’s what Shorten tweeted following the caucus meeting.

More to come.

NOW READ: Labor is expected to kill off the same-sex marriage vote today

Follow Business Insider Australia on Facebook, Twitter, and LinkedIn